"Mathematics becomes very odd when you apply it to people — one plus one can add up to so many different sums," observes physicist Werner Heisenberg in Rubicon Theatre's lucid and unexpectedly passionate revival of Michael Frayn's intellectually challenging three-hander, "Copenhagen."

Frayn is best known for his low-brow farce "Noises Off" — a dichotomy almost as hard to wrap one's head around as the scientific conundrums explored with such precision and rigor in this heady drama of ideas.

While Frayn's intricate dialogue and arguments are skillfully delivered in fine performances, Judy Hegarty Lovett's staging illuminates the play's equally important emotional truths surrounding a real-life event that had enormous stakes in the race to develop the first atomic bomb.

The few known facts are these: In 1941, as World War II raged through Europe, Heisenberg (Brett Rickaby), then the head of Germany's nuclear research program, traveled to Nazi-occupied Denmark to meet with his onetime mentor and friend, Niels Bohr (Peter Van Norden), and Bohr's wife, Marghete (Linda Purl).

The two colleagues had pioneered theoretical foundations for quantum mechanics during the 1920s, but now found themselves on opposite sides of the conflict. The meeting did not go well, and the nature of their abruptly aborted conversation has been a subject of speculation ever since.

Weaving carefully researched biographical threads, Frayn resurrects the three participants in a surreal afterlife appropriately envisioned in Trefoni Michael Rizzi's Abstract Expressionist set inspired by the paintings of Franz Kline.

As the characters offer radically different accounts and perspectives on the meeting, the stakes prove both global and personal.

Van Norden and Rickaby embody the synergy that made the two physicists such a formidable team — Bohrs the imaginative visionary, Heisenberg the practical engineer — with Purl serving as both nurturing peacemaker and ironic commentator.

As painful truths multiply like atomic fission, this shifting kaleidoscope ponders why Heisenberg wanted to meet with Bohr despite the great personal risk to them both? Was he seeking assistance with Germany's atomic weapons program, advice on delaying it, or absolution for its moral consequences? Was he as guilty in pursuing the bomb as the Allied scientists who beat him to it?

In questioning how we can make a moral judgment about anyone without some knowledge of their intentions, Frayn's play maps the quantum uncertainty principle to the heart of human nature.